Good point. I initially marked her higher because he raw faith might be impressive/intimidating to some, and make her a religious leader of sorts. However, none of the material I see seems to indicate she's at all interested in preaching or leading.
Ra might be lower. I think Christopher once said there's a reason he's not included on any official hero teams -- he's loud and arrogant and doesn't seem to get on well with others.
I dunno... Blake-Ra was an anthropologist and lives peacefully with various indigenous tribes, which takes a fair lot of social savvy and humility. He may have lost some of that when he became Ra, though. Tactics-Ra (I've seen his name mentioned somewhere, but it's not in the wiki) seems much less arrogant and more cooperative than his predecessor.
I'd say that Bunker and NightMist both deserve higher spots.
-Vance was a leader(A sargeant, I believe?) of his military unit way before he climbed into the suit. He seems like the type of officer who can give a rousing speach to his weary troops to kick them into action.
-NightMist has dealt with many a mystical being in her time. You have to be a good talker if you deal with those kind of guys for prolonged periods and not get corrupted/destroyed. And being a private investigator usually means you can talk yourself out of(or sometimes into) bad situations.
I can understand Writhe being an introvert, but I wouldn't call him a jerk per say. Nothing really leading to that on his cards either, at least from what I've noticed.
A side note: if we're allowing promo characters that make sense, where's Grandpa Legacy? :P
I'd drop Young Legacy down, she has the raw potential, but hasn't honed it yet, as you mention.
Meanwhile Tempest was a diplomat before Voss destroyed his homeworld, so he was a proffessional politician in a race of philosophers. The language barrier probably led to some troubles, but I bet he overcame that quickly enough.
Scholar seems to spend his time mentoring other people, comforting Expat, mentoring Wraith, he even has conversations with alligators, and they don't try and eat him. Also, we see him making a deal with Wager Master, I'd rank him up in tier 1 or just below.
Ignoring team leader tachyon, I don't think Tachyon would make a great talker. In the one comic issue we've seen so far (which is at the start of her career it seems) she is pre-occupied the entire time she is talking to Legacy, she moves too fast to make a full connection with other people and because she is so brilliant she may assume others follow her thinking when she is in reality leaving them in the dust. Also, her rejection of Friction led to that villain being created, she probably comes off as harsh and uptight when it comes to lab work and isn't the best at socializing, so, I'd say average at best.
Sky-scraper is dealing with a language barrier, but she also seems charming and held a high-rank in the rebellion on Dok'Thorath, so I'm not sure I would say socially inept, just dealing with severe limitations.